The present invention generally relates to water filtration apparatuses. In particular, the present invention relates to a cross-flow water filtration apparatus that includes a brine seal having a bypass. Filters to which the present invention is applicable include reverse osmosis, ultrafiltration, nanofiltration and microfiltration filters.
Typical filter apparatuses 1000 (FIGS. 1 and 2) of the prior art include one or more tubular filter assemblies 1002 housed within a tubular pressure vessel 1004. Such tubular filter assemblies have replaceable filter elements, such as a spirally wound reverse osmosis or ultrafiltration filters. Typical tubular filter assemblies 1002 are manufactured in a variety of sizes, such as 4, 6, 8 and 16 inch diameters. In operation, the tubular filter assemblies are housed within the tubular pressure vessel at elevated pressures to prevent mixing of feed and brine water with clean permeate water, as shown in FIG. 1. To maintain the effectiveness of the tubular filter assemblies and keep the cost of the filter apparatus as low as possible, the tubular filter assemblies are connected together in series within a single tubular pressure vessel. The tubular filter assemblies include a brine seal 1006 at an end of each tubular filter assembly 1002.
Brine seals 1006 are needed on the tubular filter assemblies 1002 to direct feed water into the filter element of the filter apparatus 1000 and prevent feed flow from bypassing a tubular filter assembly. Such brine seals 1006 are attached to the ends of the tubular filter assembly and preferably about its anti-telescoping device (ATD) on its feed-side to prevent the bypass of feed liquid between the tubular filter assembly 1002 and the tubular pressure vessel 1004. The brine seal is typically designed to extend or expand when feed liquid flows into the brine seal to form a water-tight seal. Such brine seals are formed from flexible rubber materials to adjust for minor tolerance differences between the internal diameter of the tubular pressure vessel and the outside diameter of the brine seal/tubular filter assembly.
The configuration of conventional brine seals is problematic, since tubular filter assemblies with conventional brine seals can only be inserted and passed through a tubular pressure vessel in a single direction. Thus, should a single tubular filter assembly need to be replaced, the entire series of tubular filter assemblies within a single pressure vessel in front of the direction of travel of the problematic tubular filter assembly would need to be removed for the exchange. In addition, conventional rubber brine seals produce a significant amount of friction when dragging/pushing the filter assembly into or out of the tubular pressure vessel. Thus, when a tubular filter assembly is particularly heavy, such as with a 16″ diameter filter assembly, it makes the removal of the tubular filter assembly difficult.
Conventional brine seals are also generally configured as a U-cup brine seal 1006. The U-cup brine seal 1006 has a bottom portion of the “U” pointing in the direction of feed flow. As such, the U-cup brine seal allows easy movement in the direction of flow of the feed liquid. That is, when the tubular filter assembly is moved in the feed flow direction, the U-cup brine seal naturally folds on itself. However, if the tubular filter assembly 1002 is pulled in the opposite direction, the U-cup brine seal will open up and create much more friction and resistance to movement in the direction opposite to the feed flow direction. Because of this issue, many plants load pressure vessels from the feed-side and remove the tubular filter assemblies from the brine-side of the tubular pressure vessel. This, however, results in a greater need for plant floor space to accommodate this type of action about both ends of the tubular pressure vessel.
Further, conventional rubber brine seals must also be lubricated to allow the tubular filter assembly to efficiently slide within the tubular pressure vessel. However, such lubricants can detrimentally contaminate the filter assembly's filter element.
Furthermore, the areas directly behind traditional brine seals are not exposed to turbulent flow conditions. Thus, the stagnant nature of fluid behind the brine seal allows for the formation of biofoul growth, which is detrimental to the operation of filter apparatus.
Accordingly, there is still a need for a filter assembly that can be loaded and removed from a pressure vessel about a single end, a filter assembly having a brine seal which reduces the amount of physical force necessary for multiple filter assembly installation and/or extraction, and eliminates the use of lubricants.